As is known, abutments provide support to the ends of a bridge superstructure near where the bridge meets an approaching path, roadway, railway or the like. There are numerous types of known abutments, with varying degrees of complexity.
FIG. 1 shows an example of a prior art abutment 101 of a bridge 104 in the example of a roadway 107 spanning over stream 106 and streambed 105. Abutment 101 retains soil, rock and other materials, generally referred to as backfill 103, from the underpass of bridge 104. The depicted configuration of abutment 101 is generally referred to as an open end, seat type abutment. Abutment stem 130 is typically a vertical standing slab of poured concrete, providing major support for bridge superstructure 140. Abutment stem 130 has an abutment backwall 120 that retains backfill 103. Abutment 101 typically also has wingwalls (not shown) to further retain backfill 103. Part of backwall 120 extends upward between bridge superstructure 140 and the approaching roadway 107.
Abutment stem 130 is supported on piles 110 driven into the ground. Depending on the design constraints of the bridge, the piles 110 are typically made of steel, reinforced concrete or timber. Alternatively, abutment stem 130 can be supported on a footing structure (not shown), such as a horizontal section of concrete.
To provide protection from adverse corrosion and erosion phenomena and provide structural support to superstructure 140 while counter the loading from backfill 103, an embankment 109 is commonly required for many bridge designs. Embankment 109 slopes from its highest point midway along abutment stem 130 down to streambed 105 of the stream 106. Abutments having such an embankment are typically referred to as being an open end abutment. Embankment 109 is usually poured concrete or stone riprap, and provides support to abutment stem 130, including support against lateral forces from backfill 103. By ensuring that the top of embankment 109 is high enough on abutment stem 130, embankment 109 protects the integrity of the foundation and support structures under abutment stem 130 by preventing penetration of water, air and other elements down the abutment wall to the underlying support structure. Such penetration may otherwise cause erosion under and around abutment stem 130, as well as corrosion or decay of materials used for piles 110 or abutment footing (not shown).
The presence of embankment 109 can be problematic in that it restricts the amount of useable space available under the bridge stream 106, or other underlying road or waterway. For a given size of an underlying road or waterway, providing space for a sufficient embankment requires increasing the span size and cost of the bridge. It would be beneficial to have a closed end abutment (i.e. without an embankment) in circumstances where prior art designs required an open end design.
The seat structure shown in FIG. 1 provides an expansion joint 127 between the bridge superstructure 140 and the abutment 101. A bridge must accommodate, in some manner, environmentally and otherwise imposed events that make its structures move relative to one another, as is known for conventional materials used to build bridges, namely steel, concrete and timber. The movements are caused, for example, by thermal changes, concrete shrinkage, creep effects, elastic post-tensioning shortening, live loading, wind, seismic events, foundation settlement, and the like. Expansion joints like expansion joint 127 accommodate both cyclic and long-term structure movements to reduce secondary stresses in the structure. Although expansion joint 127 advantageously provides expansion space necessitated by prior art materials and designs, the space adversely permits infiltration of water, air, salt and other debris down the joint into the underlying substructure components, potentially causing erosion, corrosion and mechanical failures. It would be beneficial to remove or significantly reduce the complexity or need for expansion joints from bridge abutment designs.
As is typical, expansion joint 127 is accompanied by load bearing 137. Load bearing 137 facilitates the transfer of loads from bridge superstructure 140 down to abutment 101, while restricting and/or accommodating expected forces and movements. As is known, movement allowed by adjacent expansion joint 127 must be compatible with load bearing 137, and thus the two must be designed together and in consideration of the desired behavior of the overall structure. Load bearing 137 can be a complex component, and is susceptible to corrosion, wear and mechanical disruption from debris. As such, load bearing 137 can pose problematic design challenges, increase both initial costs and ongoing maintenance costs, and raise total costs of a given bridge over the life of the structure. It would be beneficial to have a bridge that removed or reduced the need or the complexity for load bearings used with abutments.
Although reference herein is repeatedly made to abutments in the context of bridge and retaining structures, one of ordinary skill in the art will recognize that the disclosed structures and methods are applicable to abutments used for other purposes.
Needed are abutments that do not have the extent and nature of one or more of the deficiencies of prior art abutments. Needed are abutments having one or more of the following properties: lower initial costs of manufacturer, lower total costs of ownership, lower inspection and maintenance costs, lower adverse environmental impact, no or less complex load bearings, and/or no or less complex expansion joints.
The abutments used in bridges and other civil engineering structures have long been designed using traditional materials, predominantly reinforced concrete, steel and timber. Over time, the extended use and testing of these materials, and the structures built with them, has resulted in a substantial knowledge base of their material properties, and the properties of structures built with them. This knowledge base includes a relatively well developed body of standards, codes, reference material, design texts and general knowledge in the industry pertaining to the conventional materials. This body of knowledge has, in some respects, hindered the development of new designs using new materials. For example, unconventional materials, such as plastics and composites have been disfavored in part because many applicable civil engineering designers do not know or have access to the same type of knowledge base as is available for steel, concrete and timber. Unconventional materials have further been disfavored in part because of perceived, and misperceived, challenges and differences between the materials and conventional materials, such as perceived differences in strength, temperature effects, and reactions to exposure, such as the effects of prolonged exposure to sunlight. It would be advantageous to realize the benefits of new materials and new designs using such materials, while overcoming or ameliorating one or more of the deficiencies of the prior art abutments.